Authors:
Stuart Reges, Marty Stepp
Chapter:
Arraylists
Exercise:
Exercises
Question:13 | ISBN:9780136091813 | Edition: 2
Question
Write a method called reverse3 that accepts an ArrayList of integer values as a parameter and reverses each successive sequence of three values in the list. If the list has extra values that are not part of a sequence of three, those values are unchanged. For example, if a list stores values [3, 8, 19, 42, 7, 26, 19, -8] , after the call the list should store the values [19, 8, 3, 26, 7, 42, 19, -8] . The first sequence of three (3, 8, 19) has been reversed to be (19, 8, 3) . The second sequence (42, 7, 26) has been reversed to be (26, 7, 42) , and so on.
Notice that 19 and –8 are unchanged because they were not part of a sequence of three values.
Answer
Implementation of reverse3 method:
public static void reverse3(ArrayList intList)
{
for(int i = 0; i < intList.size() - 2; i += 3)
{
Integer temp1 = intList.get(i);
Integer temp2 = intList.get(i + 2);
intList.set(i, temp2);
intList.set(i + 2, temp1);
}
}